Digital Stroboscopic Holography Setup for Deformation Measurement at Both Quasi-Static and Acoustic Frequencies

Abstract

A setup for digital stroboscopic holography that combines the advantages of full-field digital holographic interferometry with a high temporal resolution is presented. The setup can be used to identify and visualize complicated vibrational patterns with nanometer amplitudes, ranging from quasi-static to high frequency vibrations. By using a high-energy pulsed laser, single-shot holograms can be recorded and stability issues are avoided. Results are presented for an acoustically stimulated rubber membrane and the technique is evaluated by means of an accuracy and a repeatability test. The presented technique offers wide application possibilities in areas such as biomechanics and industrial testing.

Application of Digital Holography for Nondestructive Testing and Metrology: A Review

“…Thus a moving interference pattern can be viewed in real time depending on the current loading of the object under test which can be continuously varied. Timeaverage and stroboscopic methods are used for investigation of vibrating surfaces [3], where time-averaging means the capture with exposure times longer than a number of vibration cycles and the stroboscopic method records repeatedly the same short phase instant of a number of periodic vibration cycles [10]. The stroboscopic illumination is provided by a pulsed laser which also is used for instant captures of dynamic processes.…”

“…For large distances, i. e. z π(ξ 2 + η 2 )/λ for all ξ, η, the Fraunhofer approximation can be applied, transfering Eq. (9) into a pure Fourier transform (10) with ν = x/(zλ), μ = y/(zλ), and A = A(ν, μ, z, λ) a complex factor not dependent on U (ξ, η). In the near field,…”

Characterization of the nonlinear elastic behavior of chinchilla tympanic membrane using micro-fringe projection

“…In some extreme cases, for instance, under blast in conflict zones, the overpressure can be as high as 100 kPa, which could cause damage to the TM (Ritenour, et al, 2008). As TM deforms under different ambient pressures, the transmission of sound energy across the middle ear can be significantly altered (Dirckx, et al, 1991; Volandri, et al, 2011; Ghadarghadar, et al, 2013; Thornton, et al, 2013; Greff, et al, 2014a, 2014b; Rosowski, et al, 2014). In efforts made to understand the effect of ambient pressure on TM function for the sound transmission, the mechanical response of TMs has been investigated under various static pressures.…”

“…Using LDV and stroboscopic holography, deformations of a human TM were measured with acoustic loading, and viscoelastic properties were determined through a hybrid method allowing FEM simulated umbo displacement to agree with the experimental measurement (De Greef, et al, 2014a, 2014b). Another full-field method to probe mechanical properties was developed to measure the TM elastic properties (Aernouts, et al, 2010; Buytaert, et al, 2009) using geometric moiré and indentation loading.…”

Multi-point vibrometer based on high-speed digital in-line holography

“…In the past, speckle interferometry (also similar to "digital image-plane holography" [36]), was demonstrated to provide an efficient tool in combination with time-averaging and digital image processing [37], fiber optics and acousto-optic stroboscopic illumination [38], laser-diode modulation [39], and pulsed laser coupled to a classical vibrometer [40]. In the past, the use of stroboscopic [41][42][43] or pulsed light [44][45][46][47][48] resulted in the direct measurement of the vibration amplitude. Such methods are quite useful for modal analysis and the determination of structural intensity [49,50], to measure 3D vibrations [40], surface acoustic wave [51], the high amplitude autooscillations of a clarinet reed [52], or 3D displacement on a cat's post-mortem tympanic membrane [53].…”